Modern diode lasers are capable of delivering very high powers at high efficiency. For example, greater than 70% efficiency has been demonstrated with powers exceeding 100 W or greater having been obtained from a diode laser bar. However, these devices tend to require the use of incoherent, multi-mode optical sources, and the corresponding beams are difficult to focus effectively onto a target surface for materials processing. Conventional laser designs rely on the use of “brightness converters,” i.e., where the light from such high efficiency diode lasers is used to pump another laser medium capable of providing a higher quality, single mode output, such as a solid-state YAG crystal or a fiber laser or amplifier. These pump lasers add cost and complexity while sacrificing efficiency, typically wasting 50% or more of the injected diode laser energy in the process of obtaining higher brightness outputs.
Optically-pumped surface-emitting lasers (OP-SEL) are an emerging laser class which combines the flexibility of quantum-well based gain materials and the beam quality of thin disk lasers. Moreover, the power can be scalable in two dimensions. Output power as high as 100 W has been demonstrated, which can be further scaled by arranging multiple semiconductor gain chips in the same cavity. One problem associated with power scaling OP-SELs is the difficulty in removing heat from the active region under optical pumping. Some examples disclosed herein provide substantially lower thermal resistance, permitting efficient, high power surface emitting laser operation. Overall efficiency of conventional OP-SELs remains relatively low as a result of inefficient pump absorption and large quantum defect between the pump and lasing wavelength. All of these need to be addressed for OP-SELs to achieve the power, efficiency and beam quality requirements for their use in a direct-diode solution for materials processing or for other applications.